Restore QGC to its normal UI layout (buttons on toolbar)

Get rid of QGCView, QGCViewPanel and FactPanel. All messages and dialogs are now handled in the root window.

TODO: Improve the experience

Move cache location methods so they are available in all builds

Add missing header

Add --clear-cache option

Fix typo

Add support for specifying fixed RTK base position

Change to case insensitive compare

Move ArduPilot preflight check handling to generic QGC

Fix mobile builds

Stable desktop version check

Remove unused code

Show the link indicator in the tool bar if two or more links are connected and at least one of them is a high latency link.
Show in the link indicator if a link is inactive.

Make all argument to AirMap queries based on what the screen shows (bounding rectangle and/or radius), respecting the limits imposed by AirMap.